Contribution of encouraging the future use of biomethane to resolving sustainability and energy security challenges: The case of the UK
Introduction
The motivation for this research came through realisation of three facts: –
- 1.
Much is said of Britain successfully decarbonising its power generation. Yet its use of natural gas (‘gas’) for power increased from 27% in 2013, to 41% in 2017 (BEIS, 2018a). Britain's gas grid reaches 90% of homes (POST, 2017), which on average consume four units of gas for every one of electricity (Ofgem, 2017).
- 2.
Heat accounts for 20% of Britain's greenhouse gas emissions (POST, 2017), driven by gas being used to generate almost 70% of heat (BEIS, 2018b). An alternative is the electrification of heat generation, but the cost of this has been estimated at £300bn (Liebreich, 2018).
- 3.
As Britain's gas production has declined; so have its net imports risen: from 33% in 2008 to 46% in 2017 (BEIS, 2018d). The winter net import share has increased from 47% in 2015 to 59% in 2018 [ibid], with winter 2018 showing “the highest recorded volume for any quarter” since records began (BEIS, 2018e). Due to its exit from the EU, Britain's future trading relationships are currently uncertain, potentially making gas imports more difficult.
It is evident that Britain is heading for major sustainability and energy security challenges if it does not change its attitude to gas consumption. The need for solutions is pressing.
Biomethane is produced via biological (anaerobic digestion) or, as Bio-SNG, thermo-chemical (gasification or pyrolysis) processes. Biomethane is typically upgraded from biogas, itself capable of being produced from waste streams like manure and food waste. Interchangeable with natural gas as a ‘drop-in substitute', it can be injected into the grid. However, it made up less than 1% of UK volume in 2017 (BEIS, 2018c). Biomethane production can result in fewer greenhouse gas emissions than natural gas (POST, 2017). It has the potential to answer the challenges.
It is clear that natural gas is set to grow its dominance of UK energy consumption. Its share of total energy consumption is predicted to rise from 68% in 2000 to 74% in 2050, predominantly driven by reduced use of oil and coal for heat production, against a background of flat or slightly reduced total energy consumption (Kannan & Strachan, 2009). The expected continued use of significant volumes of gas, despite all new and replacement gas boilers being mandated to be efficient condensing models, makes it clear that Britain's gas supply will need to emulate the success of Britain's increasingly decarbonised electricity supply.
There is a significant challenge in measuring the GHG-reducing potential of bioenergy, partly due to complex supply chains and process options (Thornley & Adams, 2018), with results frequently disputed (Welfle, Gilbert, Thornley, & Stephenson, 2017). This is very evident for biogas pathways, especially production of biomethane, as illustrated by the wide variety of GHG figures in the literature, summarised in Table 1.
Speirs et al. do not elaborate on the sources for their figures, but the wide range serves to illustrate the variety of upgrading methods, feedstocks and Life Cycle Analysis (LCA) methodologies that they, and likely the other researchers, encountered. Confidence should be attached to Tonini et al. given the wide variety of feedstocks and GHGs listed in their detailed methodology, which utilised an ISO standard, even if the upgrading technology was not evident. Giuntoli et al., however, provide full transparency on figures for multiple permutations of process options, including upgrading technologies, though they understandably limited their focus to just three feedstocks.
Despite their similar range of results, Tonini and Giuntoli do not apparently cite each other, giving assurance of independence. There is still no singular figure for biomethane, however, but it is conservative to adopt the maximum limit of audited emissions for it to qualify for the British Government's Renewable Heat Incentive (RHI) subsidy: 34.8 gCO2e/MJ, equivalent to 125.28 gCO2e/kWh (DECC, 2015). The RHI is a UK government scheme set up to encourage uptake of renewable heat technologies; the producers of biomethane receive financial incentives under the RHI scheme (POST, 2017).
Given that biomethane is a drop-in substitute for natural gas, the equivalent figures for the latter's production are important, and shown in Table 2.
Note that LNG could have been originally extracted conventionally, or non-conventionally (i.e. hydraulically fractured: ‘fracked’), though it will increasingly be the latter due to rising US production (Crooks, 2018). Speirs et al. do not specify the reason for the wide range, but the high end is likely due to non-conventional extraction and/or liquefaction.
Taking the RHI maximum for biomethane (125 gCO2e/kWh), it can be viewed that it has the potential to deliver lower GHG emissions than even the lowest figure for natural gas production (199 gCO2e/kWh). The gulf is wider still when compared with the non-conventional methods of extraction and transport that will increasingly have to be used to supply the UK as North Sea production peaks and then plummets (Bentley, 2016). Suggestions of up to 80% potential GHG reductions have been mooted for biomethane relative to natural gas (Bekkering, Hengeveld, van Gemert, & Broekhuis, 2015), though this depends upon maximum optimisation of energy efficiency and supply chain options. There will clearly be trade-offs with capital investment and production volumes. Adams suggests 60–80% is possible (Adams, 2018).
One of Stern's ‘co-benefits’ of investing in low-carbon energy is the reduction of “short lived pollutants, including soot [and] methane” (Stern, 2015, p. 263) and this he relates to the production of natural gas. Methane emissions also occur during the production of biomethane, however, and it is referred to as ‘methane slip’. A paper cited by many researchers in the field concludes that upgrading biogas to biomethane may be an environmentally beneficial alternative to biogas combustion in on-site CHP when considering global and local emissions (Ravina & Genon, 2015). However, they caution a strong sensitivity to methane slip during upgrading. If slip is limited to 0.05% they conclude that it represents just 2% of the total GHG footprint of the end-to-end biomethane production process. But if slip reaches 1.4%, then its share boosts to a 40% share, and to a 66% share if it reaches 4%. The researchers conclude that reaching this 4% point would mean that on-site CHP combustion would instead be the most sustainable biogas pathway.
The question of how much methane slip occurs during upgrading is therefore critical. It would seem logical that the quality of plants' initial installation and subsequent maintenance would have a bearing on methane emissions. It is evident that the chosen upgrading technology has a strong bearing, and the literature on the major ones is summarised in Table 3.
For the UK specifically, membrane separation, which also exhibits the lowest power consumption (Adams, 2018), is used in the majority of plants (Horschig, Adams, Röder, Thornley, & Thrän, 2016), (Bates et al., 2014). It would therefore be reasonable to suggest that UK production is likely within Ravina and Genon's threshold of 4% methane slip.
Poeschl et al. (Poeschl, Ward, & Owende, 2012) suggest that even 3% methane slip cancels out the climate change benefits of biomethane substituting natural gas. This possibly ignores, however, that natural gas production also involves the loss of methane. Stern (2015), citing (IEA, 2013) suggests that 280 MtCO2e could be saved annually by elimination of the venting and flaring of methane in natural gas production. Venting is far worse, as it is the release of non-combusted methane, which has a Global Warming Potential of 21 times that of CO2 (Smil, 2015). The US EPA suggested in 2011 that just 0.47% of US natural gas was leaked during production, but a credible paper, published in June 2018, upgraded that figure to 2.3% (Alvarez et al., 2018).
Opinions differ on the relative increase of methane leaks related to fracking over conventional production but one instrumented-aerial survey of the huge Marcellus shale suggested them being two to three times greater than that expected for conventional drilling (Smil, 2015). This is significant as fracking is expected to boost US 2018 production by 10% year-on-year, and grow 60% by 2030 (Yergin & Andrus, 2018). This US shale gas, exported as LNG, will become increasingly important to satisfying UK demand (Sharples, 2018).
Within the context of the UK, the specific objectives of this research are to: –
- 1.
Explore the views of market players on the dynamics of the market, and what is necessary for its expansion.
- 2.
Critically evaluate how more grid biomethane could economically help meet Britain's challenges, compared to the alternatives.
- 3.
Recommend ways to overcome the barriers preventing biomethane from meaningfully contributing to Britain's challenges.
The outcome is a clear picture of where Britain is, and could be, regarding its use of grid biomethane, and the extent to which this could meet Britain's challenges.
This research has value through its contribution to the knowledge of the nascent UK biomethane industry, currently funded by British taxpayers. An industry that aims to reduce the dependence on the decreasingly productive North Sea fields that provide a dominant proportion of Britain's power and heat. It also aims to help solve arguably Britain's toughest decarbonisation challenge: at just 7% of heat produced, the UK is third-from-last in the EU for renewable heat (Eurostat, 2018).
Section snippets
Method
The research strategy for objective one involved semi-structured interviews with 19 key UK market participants, spanning biomethane producers, retail energy suppliers, network operators, trade bodies, business users; plus a policymaker. The strategy lent itself well to the exploratory nature of the objective and structured interviews allow for direct comparison of participants' answers whilst allowing for clarificatory questions. They also maximise the likelihood of responses and quotable
Stakeholders' perspectives
The semi-structured interviews provided an opportunity to gauge the feelings of practitioners and policymakers. This included quantitatively via questions that requested that they choose scores on a scale of one (most negative) to ten (most positive). All interviewees scored their sentiment firstly on the current health of the UK marketplace, and secondly on the outlook with a 5–10 year horizon.
The biomethane producers' underpinning scores were relatively optimistic, with 80% showing a static
Market dynamics
It is likely that for biomethane to become economically sustainable in the UK some market pull – demand from consumers – for a premium product would need to become apparent. This is more so in the absence of strong government policies such as a carbon tax – an economic instrument – or a blend-in mandate. Market pull would be influenced by consumers being aware of green gas, but also by the level of retail price differential compared to natural gas.
To measure this current price differential, a
Environmental sustainability
This research reviewed the underlying dataset of National Grid's most recent annual ‘Future Energy Scenarios’ study (National Grid, 2018). This provided four parallel futures for the UK electricity and gas ecosystems, from both supply and demand standpoints. The dataset provides suggested annual levels of demand for gas, and supply from UK conventional, UK shale, European, LNG and finally UK biomethane sources, up to 2050. In its 2018 annual report to Parliament, the Committee on Climate Change
Conclusion and policy implications
The research interviewees' unease towards a lack of a British Government announcement to extend the Renewable Heat Incentive (RHI) for new entrants beyond 2021 was palpable. Uncertainty about the level of RHI subsidies following the 2017 General Election caused a hiatus in new project development, and today the scheme's impending closure has killed new applications. The interviewees held equally strong views towards government policy efforts more broadly, and the synthesis of these helped form
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